Conventional horseshoes are constructed of steel, iron or aluminum and are fastened to the underside of a hoof by nails. Such horseshoes have a U-shaped configuration to permit the natural outward movement of the outer side wall of an animal's hoof upon impact with a surface. The spreading is a result of the elastic characteristics of a hoof and is most pronounced at the rear, or heel, of a hoof. This spreading is important to prevention of injuries. While the conventional U-shaped configuration does permit spreading despite the inelastic nature of the metal horseshoe, the conventional horseshoe is heavy and does little to absorb impacts.
Horseshoes are typically secured to a hoof by the driving of nails into the horn wall of the hoof, known as the keratinous portion of the hoof. Great care must be taken in directing the nail into the keratinous portion so as to prevent injury to the animal. The nails are driven in a direction at an angle away from the center of the hoof, with any nail points extending from the outer side wall of the hoof being cut off or hammered against the hoof. Errors made in driving the nails or in hammering nail points may lame an animal.
Horseshoes made of a plastic material are known. Such horseshoes are disclosed in U.S. Pat. Nos. 4,206,811 to Dallmer, 3,603,402 to McDonnell, 3,519,079 to Bieber and 3,302,723 to Renkenberger et al. Dallmer, for example, teaches a plastic horseshoe having a dovetailed groove which receives a metal strip. The metal strip creates a resilient resetting force when the free ends of the horseshoe-shaped plastic body are drawn apart for the purpose of mounting a plastic body on a larger hoof. Plastic horseshoes provide a lighter weight, more comfortable protection to an animal's hoof. Moreover, a plastic horseshoe is more resilient and compressible against a hoof than a conventional metal horseshoe.
One difficulty associated with the use of horseshoes made of a plastic material is that of securely fixing the shoe to a hoof. Typically, the plastic horseshoe is fixed to the hoof by an adhesive. However, because of the mass of a horse, the adhesive bonding is subjected to extreme forces. Dallmer includes a vertically extending wall which may be fixed to the side of the hoof to better prevent rearward sliding of the plastic horseshoe. Adhesively bonded plastic horseshoes, however, are still susceptible to extreme forces which promote forward or lateral movement of the horseshoe relative to the hoof. Additionally, the choice of adhesive is critical. The adhesive may cause irritation of the hoof, thereby promoting "hoof rot", or thrush, in the white line area of the hoof.
U.S. Pat. No. 3,285,346 to Jenny et al. teaches a method of producing an elastic horseshoe directly onto an animal's hoof. The hoof is drilled with a number of bores and then placed in a mold. Plastic material is then inserted into the mold. After hardening of the material, the mold is removed. While this method eliminates the need of adhesive, the drilling of bores into the hoof entails many of the same dangers involved with the nailing of shoes onto a hoof.
It is an object of the present invention to provide a plastic horseshoe and a method of affixing the plastic horseshoe to the hoof of a horse, mule or the like without risk of injury to the animal. It is a further object to provide such a shoe which guards against dislodgment regardless of the direction of frictional force on the shoe relative to the hoof.